1. Technical Field
The present invention relates to a color filter and a manufacturing method for the color filter and, more particularly, to a manufacturing method based on an ink jet processing method.
2. Description of the Related Art
A color filter is an important element of a liquid crystal display (LCD). The color filter is used for improving picture quality and providing a primary color to each sub-pixel of the LCD.
Referring to FIG. 8, a first conventional color filter 20 includes a glass substrate 22, a black matrix 24 formed on a surface of the glass substrate 22, a color layer formed of red (R) color portions, green (G) color portions and blue (B) color portions, and a transparent electrically conductive layer 28 covering the black matrix 24 and the color layer. The black matrix 24 defines a plurality of sub-pixels of the color filter 20. Every sub-pixel accommodates one color portion chosen from R, G, and B color portions. The color filter 20 is generally manufactured via a method called “pigment-dispersion method”. A normal process of the pigment-dispersion method has four repeated cycles. Wherein, each cycle contains a spin coating process or a slit coating process for one selected color, a pre-bake and exposing process to solidify the selected color position to be a uniform color layer, a developing process to transform the uniform color layer to be a patterned film, and a heating process to transform the patterned film to be a solidified layer. After one color cycle is finished, another color cycle is performed. Therefore, four cycles are repeated to be the black matrix, the red color layer, the blue color layer, and the green color layer. Since, total processing steps will be more than 25 steps, the processing cost is high.
A newer manufacturing method for color filters called “ink jet processing method” is developed in few years. Referring to FIG. 9, a second conventional color filter 10 made by the ink jet processing method includes a glass substrate 12, a black matrix 14 formed on a surface of the glass substrate 12, a plurality of banks 16 superposed on the black matrix 14, a color layer formed of R, G, and B color portions, an overcoat layer 17 covering the banks 16 and the color layer, and a transparent electrically conductive layer 18 covering the overcoat layer 17. The black matrix 14 defines a plurality of sub-pixels of the color filter 10. The banks 16 and the black matrix 14 enclose a plurality of spaces each for accommodating one color portion chosen from R, G, and B color portions. This structure is often seen if the manufacturing method is the ink jet processing method. The banks 16 are especially useful in order to prevent adjacent ink from being mixed during manufacturing.
The ink jet processing method mainly includes a step of jetting ink drop by drop onto a transparent substrate by an ink jet head to deposit the ink on a prescribed space. Then the ink in the space is dried and becomes a color portion. The ink jet processing method simplifies the manufacturing process of the color filters and reduces production cost. In order to ensure the uniformity of the color portions, each space must be jetted into a consistent amount of the ink. For example, each of the spaces is jetted into equal drops of the ink.
However, during the jetting process, the ink jet head maybe does not jet for some reason, though the ink jet head ought to jet. In addition, the volume of a jetted drop maybe does not equal to the standard volume of a drop, for example, when a drop of the ink contains air bubble. These can cause the nonuniformity of the color portions, even cause the defects of the color filter.
What is needed, therefore, is a color filter with a good uniformity of color portions, and a manufacturing method that can improve the quality of the color filter.